Electrical contact devices, particularly terminal blocks, have been known in the art for decades and are used in their millions for the wiring of electrical systems and equipment. Terminal blocks are usually latched onto mounting rails, a multiplicity of which is usually disposed in turn in a switch cabinet. Known contact connections in electrical contact devices include screw-type terminals, tension spring terminals, cutting terminals or plug contact connections, particularly in the form of bushing or tulip contacts.
In addition, electrical contact devices are known in which at least a first contact connection is created by terminal legs for connection to a conductor plate and a second contact connection is formed as a plug connection for a plug connector.
Electrical contact devices should usually produce a current flow between two separate contact elements. In order to connect the contact elements, the electrical contact devices therefore have at least two contact connections, which are electrically connected to one another via a connection piece.
Apart from the aforementioned basic type of terminal blocks, there is also a multiplicity of different types of terminal block, which are specially adapted to suit each individual application. Given here by way of example are double-level or triple-level terminals and also three-conductor or four-conductor terminals, which then each have a correspondingly larger number of conductor connection elements designed as contact connections. In addition, there are terminal blocks consisting of a basic terminal and a connection plug, wherein the basic terminal has a terminal housing, at least one conductor connection element designed therein as a contact connection and also at least one other contact connection electrically connected to the conductor connection element and designed as a slot. The connection plug likewise has at least one conductor connection element and a plug contact electrically connected to the conductor connection element. With this type of terminal block, the basic terminal is usually first latched onto a mounting rail and the connection plug is then attached with its plug contact to a corresponding slot in the basic terminal.
All the aforementioned electrical contact devices, such as the terminal block, the electrical contact device for connecting to a circuit board, the basic terminal and the connection plug have a housing made from insulating material, in which a contact group with two contact connections is mounted and secured.
Rigorous requirements are made of the contact group's attachment within the housing, in order to prevent the contact group from becoming detached from the housing, leaving the user directly exposed to the live contact group. There is a particular risk of this happening when a contact element connected to one of the contact connections is forcibly removed. In order to secure the contact group within the housing, it is known from DE 27 13 894 A1, for example, that locking means can be provided on the contact group and inside the housing. This sort of attachment has already proved itself in practice. One perceived disadvantage of this sort of electrical contact device is that a reliable connection between the contact group and the housing only exists if it is actually locked to the housing. In order to guarantee this locking mechanism, the connection must be inspected following production of the contact device.